There's a great way to combine history and health in Key West. Put on your walking shoes and spend 1 to 2 hours walking the Pelican Path Self-Guided Tour of Key West.
As their website states, you'll "explore and wander at leisure through Key West’s colorful history along the charming streets of Old Town." But you'll do it at your own pace and in your own time.
Go to http://oirf.org/page.php?p=pelican for more information and to print out directions for the tour which is sponsored by the Old Island Resoration Foundation.